Shantha prime

A Shantha primep is a prime number of the form p=3q-2 with q being a Mangammal prime (http://planetmath.org/MangammalPrime). The smallest Shantha prime is 7=32-2. The next is 3541-2 and has 259 digits. Shantha primes are very rare among the smaller numbers. The above formulation generates mostly composite numbers.